Pixlr.com is a web-based program which means there's nothing to download. It allows to you to have various layers and supply different styles (ie drop-shadow, glow). You can open PSD files in Pixlr and it maintains the layers, including text layers, however you lose the ability to edit the text. This means if you need to add or change text you must add it yourself. The following video highlights the aforementioned items.
Pixlr Tutorial: How to Make a Banner (using layers, style options, and free transform)
Gimp is a very powerful program. It has very similar capabilities to Photoshop with one major difference, it's free. This open-source software has many tools and features (more than Pixlr). The following video does a good job of helping someone get started in Gimp. It's kind of long (10:57) but it explain layers, adding a background, adding text and applying effects, and saving files in Gimp.
GIMP Basics - Introduction + Beginner tutorial example
There are many other tutorial videos available on both of the pieces of software. So if you start using them and think "I wonder if I could.." do some searches and check them out.
EM-S ISD Webmasters this video is for you! Edit PSD in Pixlr
